Foreign Ministry spokeswoman Le Thi Thu Hang said Thursday that authorities were trying to confirm whether China’s Dongfang 13-2 CEPB oil rig is functioning within Vietnamese waters in the Gulf of Tonkin in the East Sea, known internationally as the South China Sea.

On Sunday, the Xinhua news agency reported that "Dongfang 13-2 CEPB," the second largest offshore oil production and processing platform in China, was completed for shipment and would be shipped to the Yinggehai Basin on Wednesday.

Yinggehai Basin lies at the southern end of the Red River fault zone, between the Vietnamese coast and China's Hainan Island.

Hang said the Sino-Vietnamese Agreement on Maritime Boundary Delimitation in the Gulf of Tonkin (2004), which clearly defines the areas and legality of China and Vietnam’s territorial waters, exclusive economic zones and continental shelves, is in accordance with international law, including the 1982 United Nations Convention on the Law of the Sea.

"The two countries have the responsibility to seriously follow the agreement in terms of managing, utilizing and protecting resources within each country’s exclusive economic zones and continental shelves, for the benefit of each country and for peace and stability within the South China Sea," she said.

Dongfang 13-2 CEPB oil rig was built by China's Offshore Oil Engineering Co., Ltd. with a floating weight of more than 17,000 tons and covers an area of a football field, according to Xinhua. It is expected to go functional in June.